edu.emory.mathcs.backport.java.util
Interface NavigableSet

All Superinterfaces:

java.util.Collection, java.lang.Iterable, java.util.Set, java.util.SortedSet

All Known Implementing Classes:

ConcurrentSkipListSet, TreeSet

public interface NavigableSet
extends java.util.SortedSet

A SortedSet extended with navigation methods reporting closest matches for given search targets. Methods lower, floor, ceiling, and higher return elements respectively less than, less than or equal, greater than or equal, and greater than a given element, returning null if there is no such element. A NavigableSet may be accessed and traversed in either ascending or descending order. The descendingSet method returns a view of the set with the senses of all relational and directional methods inverted. The performance of ascending operations and views is likely to be faster than that of descending ones. This interface additionally defines methods pollFirst and pollLast that return and remove the lowest and highest element, if one exists, else returning null. Methods subSet, headSet, and tailSet differ from the like-named SortedSet methods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Subsets of any NavigableSet must implement the NavigableSet interface.

The return values of navigation methods may be ambiguous in implementations that permit null elements. However, even in this case the result can be disambiguated by checking contains(null). To avoid such issues, implementations of this interface are encouraged to not permit insertion of null elements. (Note that sorted sets of Comparable elements intrinsically do not permit null.)

Methods subSet(E, E), headSet(E), and tailSet(E) are specified to return SortedSet to allow existing implementations of SortedSet to be compatibly retrofitted to implement NavigableSet, but extensions and implementations of this interface are encouraged to override these methods to return NavigableSet.

This interface is a member of the Java Collections Framework.

Since:

1.6

Author:

Doug Lea, Josh Bloch

Method Summary

java.lang.Object	ceiling(java.lang.Object e) Returns the least element in this set greater than or equal to the given element, or null if there is no such element.
java.util.Iterator	descendingIterator() Returns an iterator over the elements in this set, in descending order.
NavigableSet	descendingSet() Returns a reverse order view of the elements contained in this set.
java.lang.Object	floor(java.lang.Object e) Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.
java.util.SortedSet	headSet(java.lang.Object toElement)
NavigableSet	headSet(java.lang.Object toElement, boolean inclusive) Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement.
java.lang.Object	higher(java.lang.Object e) Returns the least element in this set strictly greater than the given element, or null if there is no such element.
java.util.Iterator	iterator() Returns an iterator over the elements in this set, in ascending order.
java.lang.Object	lower(java.lang.Object e) Returns the greatest element in this set strictly less than the given element, or null if there is no such element.
java.lang.Object	pollFirst() Retrieves and removes the first (lowest) element, or returns null if this set is empty.
java.lang.Object	pollLast() Retrieves and removes the last (highest) element, or returns null if this set is empty.
NavigableSet	subSet(java.lang.Object fromElement, boolean fromInclusive, java.lang.Object toElement, boolean toInclusive) Returns a view of the portion of this set whose elements range from fromElement to toElement.
java.util.SortedSet	subSet(java.lang.Object fromElement, java.lang.Object toElement)
java.util.SortedSet	tailSet(java.lang.Object fromElement)
NavigableSet	tailSet(java.lang.Object fromElement, boolean inclusive) Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement.

Methods inherited from interface java.util.SortedSet

comparator, first, last

Methods inherited from interface java.util.Set

add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, remove, removeAll, retainAll, size, toArray, toArray

Method Detail

lower

java.lang.Object lower(java.lang.Object e)

Returns the greatest element in this set strictly less than the given element, or null if there is no such element.

Parameters:

e - the value to match

Returns:

the greatest element less than e, or null if there is no such element

Throws:

java.lang.ClassCastException - if the specified element cannot be compared with the elements currently in the set

java.lang.NullPointerException - if the specified element is null and this set does not permit null elements

floor

java.lang.Object floor(java.lang.Object e)

Returns the greatest element in this set less than or equal to the given element, or null if there is no such element.

Parameters:

e - the value to match

Returns:

the greatest element less than or equal to e, or null if there is no such element

Throws:

java.lang.ClassCastException - if the specified element cannot be compared with the elements currently in the set

java.lang.NullPointerException - if the specified element is null and this set does not permit null elements

ceiling

java.lang.Object ceiling(java.lang.Object e)

Returns the least element in this set greater than or equal to the given element, or null if there is no such element.

Parameters:

e - the value to match

Returns:

the least element greater than or equal to e, or null if there is no such element

Throws:

java.lang.ClassCastException - if the specified element cannot be compared with the elements currently in the set

java.lang.NullPointerException - if the specified element is null and this set does not permit null elements

higher

java.lang.Object higher(java.lang.Object e)

Returns the least element in this set strictly greater than the given element, or null if there is no such element.

Parameters:

e - the value to match

Returns:

the least element greater than e, or null if there is no such element

Throws:

java.lang.ClassCastException - if the specified element cannot be compared with the elements currently in the set

java.lang.NullPointerException - if the specified element is null and this set does not permit null elements

pollFirst

java.lang.Object pollFirst()

Retrieves and removes the first (lowest) element, or returns null if this set is empty.

Returns:

the first element, or null if this set is empty

pollLast

java.lang.Object pollLast()

Retrieves and removes the last (highest) element, or returns null if this set is empty.

Returns:

the last element, or null if this set is empty

iterator

java.util.Iterator iterator()

Returns an iterator over the elements in this set, in ascending order.

Specified by:

iterator in interface java.util.Collection

Specified by:

iterator in interface java.lang.Iterable

Specified by:

iterator in interface java.util.Set

Returns:

an iterator over the elements in this set, in ascending order

descendingSet

NavigableSet descendingSet()

Returns a reverse order view of the elements contained in this set. The descending set is backed by this set, so changes to the set are reflected in the descending set, and vice-versa. If either set is modified while an iteration over either set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined.

The returned set has an ordering equivalent to Collections.reverseOrder(comparator()). The expression s.descendingSet().descendingSet() returns a view of s essentially equivalent to s.

Returns:

a reverse order view of this set

descendingIterator

java.util.Iterator descendingIterator()

Returns an iterator over the elements in this set, in descending order. Equivalent in effect to descendingSet().iterator().

Returns:

an iterator over the elements in this set, in descending order

subSet

NavigableSet subSet(java.lang.Object fromElement,
                    boolean fromInclusive,
                    java.lang.Object toElement,
                    boolean toInclusive)

Returns a view of the portion of this set whose elements range from fromElement to toElement. If fromElement and toElement are equal, the returned set is empty unless fromExclusive and toExclusive are both true. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.

The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.

Parameters:

fromElement - low endpoint of the returned set

fromInclusive - true if the low endpoint is to be included in the returned view

toElement - high endpoint of the returned set

toInclusive - true if the high endpoint is to be included in the returned view

Returns:

a view of the portion of this set whose elements range from fromElement, inclusive, to toElement, exclusive

Throws:

java.lang.ClassCastException - if fromElement and toElement cannot be compared to one another using this set's comparator (or, if the set has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception if fromElement or toElement cannot be compared to elements currently in the set.

java.lang.NullPointerException - if fromElement or toElement is null and this set does not permit null elements

java.lang.IllegalArgumentException - if fromElement is greater than toElement; or if this set itself has a restricted range, and fromElement or toElement lies outside the bounds of the range.

headSet

NavigableSet headSet(java.lang.Object toElement,
                     boolean inclusive)

Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.

The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.

Parameters:

toElement - high endpoint of the returned set

inclusive - true if the high endpoint is to be included in the returned view

Returns:

a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement

Throws:

java.lang.ClassCastException - if toElement is not compatible with this set's comparator (or, if the set has no comparator, if toElement does not implement Comparable). Implementations may, but are not required to, throw this exception if toElement cannot be compared to elements currently in the set.

java.lang.NullPointerException - if toElement is null and this set does not permit null elements

java.lang.IllegalArgumentException - if this set itself has a restricted range, and toElement lies outside the bounds of the range

tailSet

NavigableSet tailSet(java.lang.Object fromElement,
                     boolean inclusive)

Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.

The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.

Parameters:

fromElement - low endpoint of the returned set

inclusive - true if the low endpoint is to be included in the returned view

Returns:

a view of the portion of this set whose elements are greater than or equal to fromElement

Throws:

java.lang.ClassCastException - if fromElement is not compatible with this set's comparator (or, if the set has no comparator, if fromElement does not implement Comparable). Implementations may, but are not required to, throw this exception if fromElement cannot be compared to elements currently in the set.

java.lang.NullPointerException - if fromElement is null and this set does not permit null elements

java.lang.IllegalArgumentException - if this set itself has a restricted range, and fromElement lies outside the bounds of the range

subSet

java.util.SortedSet subSet(java.lang.Object fromElement,
                           java.lang.Object toElement)

Equivalent to subSet(fromElement, true, toElement, false).

Specified by:

subSet in interface java.util.SortedSet

Throws:

java.lang.ClassCastException

java.lang.NullPointerException

java.lang.IllegalArgumentException

headSet

java.util.SortedSet headSet(java.lang.Object toElement)

Equivalent to headSet(toElement, false).

Specified by:

headSet in interface java.util.SortedSet

Throws:

java.lang.ClassCastException

java.lang.NullPointerException

java.lang.IllegalArgumentException

tailSet

java.util.SortedSet tailSet(java.lang.Object fromElement)

Equivalent to tailSet(fromElement, true).

Specified by:

tailSet in interface java.util.SortedSet

Throws:

java.lang.ClassCastException

java.lang.NullPointerException

java.lang.IllegalArgumentException